Today, regardless of where you place the blame (my money is on a juiced ball), baseball is on track to shatter nearly every dinger-related record. So in our third consecutive year of increasing offense, our attention now turns to the players serving up those homers: When and how will pitchers adjust to the fact that so many batters are launching shots over the fences?

For a long time, the strategy for facing a slugger was clear. “The best way to limit slugging percentage was to throw down and away and off the plate,” said former MLB catcher and current Chicago Cubs coach John Baker. Baker played from 2008 to 2014, at a time when the bottom was falling out of the strike zone and offense was dropping with it. In 2013, 36.5 percent of throws crossed the plate less than two feet off the ground, and hitters racked up a slash line of just .210/.295/.298 against those pitches. Meanwhile, hitters did considerably better against pitches more than three feet above the plate: .210/.351/.348.

Then the league adjusted. More recently, “the guys that are the best guys in the world right now all seem to have this [Mike] Trout-type low-ball swing,” Baker said. Nowadays, the same low pitches that once got hitters out are getting slugged at a rate 20 points higher than in 2013 (.212/.301/.321). While production high in the zone is still decent (.203/.351/.362), the gap between the two types of pitches has closed significantly.1 It seems as though a wave of young players entered the league with their swings geared to combat the knee-high strike, and that trend reduced the pitch’s effectiveness.

But for every hole in the zone that the league’s batters close, another one opens. “It goes in waves, the pitching changes its philosophy, and the hitting changes up, and the pitching adjusts, and on and on,” Baker said. With batters adopting uppercut swings to generate loft even on low pitches, it stands to reason that pitchers could go even higher in response. Previous research has shown that when a fly-ball hitter meets a high strike, the result is often a popup or weak contact. I looked at the median height of all four-seam fastballs month by month to see whether pitchers are giving that strategy a try.

By and large, hurlers have adopted the elevated approach. But the home run surge began in 2015, and fastball height only started increasing noticeably this July. Even as recently as 2016, when home runs were up about 15 percent compared to 2015, it appeared that pitchers were still aiming low in the zone. Complicating matters, the strike zone has been shrinking at the bottom. In the last few months, umpires have been more reluctant to call strikes down at the knees, bringing the strike zone closer to its 2013 height. It might be that pitchers are adjusting upwards in reaction to fewer low strike calls, rather than anything hitters are doing.

There’s no question that the low-strike strategy is entrenched. “They’ve taught the same thing in pitching for a hundred years: Be down, and they hit the ball on the ground,” said Chicago Cubs pitcher Jon Lester. Lester has had an above-averageground ball rate over his career, but his ERA has spiked this season to 4.03. But pitchers across the league are giving up more runs this year, and as a result, Lester is on pace for similar levels of overall production (as measured by wins above replacement) as he generated last year. Because the dinger revolution seems to be affecting everyone equally, pitchers including Lester and Los Angeles Dodgers ace Clayton Kershaw are seeing career highs in long balls allowed even though they’re matching their career norms in value. Cubs swingman Mike Montgomery pinned some of the reluctance to adjust on the evenness of the change across the league: “The thing is, it’s a fair playing field.”

Lester said that he sometimes makes height adjustments for specific hitters, but only one or two guys per lineup. He declined to name an opposing batter who he would target this way, but said that his teammate Ian Happ might be a candidate if Lester ever faced his fellow Cub. Armed with better scouting reports than the public has available, pitchers might be revising their approach to deal with the home run surge on a player-by-player basis, in ways that wouldn’t move the overall median pitch height very much.

While pitchers have been slow to expand the zone upwards, they have adjusted in other ways. Four-seam fastballs are usually the pitch of choice to generate pop-ups, since they naturally rise (relative to other pitches). Baker characterized MLB as moving from a “sinker/slider” league to “reverting back to the fastball/curveball game it was before.”

The use of four-seam fastballs was declining for years until the home run surge began. Since September 2014 (the lowest point in the usage of four-seam fastballs), pitchers are throwing about 10 percent more four-seamers. In addition to leading to fly balls, heater usage is also associated with additional swinging strikes compared to sinkers. As allowing contact becomes increasingly dangerous for pitchers, it make sense that they’d aim to keep the batter from touching a pitch, which might be the surest way to limit the damage.

There is no one-size-fits-all strategy to avoiding home runs. “Everything is specific to individual situations,” Baker said. A high fastball might work well against some batters, but it might also be the wrong move in some contexts. With the breeze blowing out at Wrigley, even a weak fly ball has a chance at making it over the fence, so the optimal pitching strategy varies from day to day.

Still, the increase in home runs demands new tactics, even on windy days. Between the shifting strike zone, evolving hitting philosophies and changes to the ball, the league is challenging pitchers to adjust to several new factors at once. “That’s the fun part,” Montgomery said. “How are you going to be the one to adapt and survive?”

If all else fails, they could just raise the mounds again.

Footnotes

Data is up to date through July 17, 2017.

Rob Arthur is FiveThirtyEight’s baseball columnist and also writes about crime. @No_Little_Plans